1. Field of the Invention
The present invention relates to a fixing device for wet-type electrophotographic copying machines or especially for wet-type electrophotomechanical machines.
2. Prior Art
Generally, wet-type electrophotographic copying machines and wet-type electrophotomechanical machines are constructed to carry out the steps of developing an electrostatic latent image on a photosensitive sheet of paper with a liquid developer in a liquid development device, squeezing out the liquid developer off the photosensitive sheet, and fixing the visualized image on the sheet in a fixing device. Fixing devices used for the wet-type electrophotographic copying machines or electrophotomechanical machines are of the air-dried type or thermal fusion type, the latter being composed of a heat source such as a lamp and a fan for blowing air heated by the lamp against the photosensitive sheet. While the sheet which is fed from the squeeze device is being transported on a feed belt or a transport device comprising a guide plate and feed rollers, hot air is applied against the photosensitive sheet to dry the same and at the same time to fix the image on the photosensitive sheet. Such thermal fusion type fixing devices are increasingly equipped in wet-type electrophotomechanical machines for producing printing masters to thereby improve printing endurance thereof, and developers are being developed which will be best fit for the thermal fusion type fixing devices. In such fixing devices, however, only one lamp is normally insufficient for fusing the developer, and two lamps, while generating enough heat to fuse the developer, tend to brown or burn the photosensitive sheet when it becomes jammed in the fixing device and is caused to stay exposed directly to the illuminating lamps. With the direct-exposure lamps, it would be difficult to control temperatures as with a thermostat since the thermostat would be likely to be energized to switch off the lamps during movement of the photosensitive sheet, resulting in unthorough fixing. Furthermore, radiant heat produced from the heat source is so intensive that the temperature in the machine will rise to the point where the machine as a marketable product can be deemed unsatisfactory.
Some of the wet-type electrophotomechanical machines are sold as ITEK 135, 136 by ITEC International Inc., such machines having fixing devices which use three lamps rated 1 KW.
The electrophotomechanical machines are used mostly by printers who make a multiplicity of prints for their business and hence require printed images of high quality.